JPH0565959A - Metal gasket and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a metal gasket that keeps off any damage to a metal material at the time of forming a turnup part and after being clamped, and expands the range of material selection for an elastic metal plate by forming a specified area to be related to the turnup part of the elastic metal plate at time of forming this turnup part, and its manufacture. CONSTITUTION:In a turnup part 5 of an elastic metal plate 3 constituting a metal gasket, an inner part area of a turnup edge part 7 and an area where a turnup tip 13 is situated are thinned from the turnup side. At the turnup edge part 7 being folded, bending is gentle and there is a clearance 14 in the inner part, and since the turnup tip 13 is a hollowed surface 8, it will not come into contact with the elastic metal plate 3 at all. Even if a selective material is widened to some extent, cracks and creases are not produced in the turnup edge part 7, and after clamping, the tip 13 will not scratch the elastic metallic plate 3 at all.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine, and more particularly to a metal gasket used for sealing between opposing mounting surfaces of a cylinder head and a cylinder block in a multi-cylinder internal combustion engine and a method of manufacturing the same.

[0002]

2. Description of the Related Art Heretofore, a metal gasket made of a metal material has been used to seal between opposing mounting surfaces of a structural member of an internal combustion engine, such as between a cylinder head and a cylinder block. The metal gasket generally has a bead in the vicinity of the periphery of the through hole corresponding to the cylinder bore, water, and oil passages of the structural member, and when the cylinder head and the cylinder block are fastened and fixed with bolts, the bead is An elastic annular contact portion is formed with respect to the opposing mounting surfaces to seal the opposing mounting surfaces around the through hole.

However, recent internal combustion engines are required to have a high output and a light weight, and as a part thereof, a cylinder head, a cylinder block, etc. are made of conventional steel having a large specific gravity,
There is a tendency to use an aluminum material having a small specific gravity instead of a casting. Although the aluminum material is lightweight, it has low rigidity, which may cause inconvenience when tightening the metal gasket and operating the internal combustion engine. That is, since the tightening bolt positions of the metal gasket are dispersed in the outer peripheral portion or the relatively outer peripheral portion of the metal gasket and are not necessarily evenly distributed around the cylinder bore hole, these structures having reduced rigidity When the opposing mounting surfaces between the materials are tightened with the tightening bolts through the single-plate metal gasket, the opposing mounting surfaces are likely to be irregular. As a result, high-temperature and high-pressure combustion gas penetrates between the opposing mounting surfaces at locations with large strain, such as the portion between the cylinder bore holes, and corrodes the bead portion of the metal gasket interposed between the opposing mounting surfaces. Stain and reduce the sealing effect.

Furthermore, since the rigidity of these structural materials decreases, the relative displacement of the cylinder head with respect to the cylinder block increases during the operation of the internal combustion engine, and the distance between the cylinder head and the cylinder block repeatedly increases and decreases. Further, since the temperature change of the metal gasket greatly changes depending on the operation and stop of the internal combustion engine, repeated stress, that is, mechanical stress and thermal stress also acts on the metal gasket. This load fluctuation stress is generated as a large value in the lowest rigidity portion of the cylinder block or the cylinder head, and as a result, there is a problem that the bead is settled or a crack is generated to deteriorate the sealing performance.

With respect to such a metal gasket, the present applicant has already filed an application regarding a single-plate metal gasket which is arranged between the mounting surfaces of a cylinder head and a cylinder block of an internal combustion engine and is tightened, and a method for manufacturing the same. (Japanese Patent Application No. 2-306295). With regard to this metal gasket, a cylinder bore hole formed in an elastic metal plate, a bead formed along the cylinder bore hole, spaced radially outward from the periphery of the cylinder bore hole, and a bead formed around the cylinder bore hole. Since the metal plate has a folded-back portion formed by folding back outward in the radial direction on the convex side, and the folded-back portion of the metal plate is molded and heat-treated, it is clamped and pressed between the opposing mounting surfaces. Then, the bead forms an annular seal line with respect to the opposing mounting surface, and at the same time, the folded portion having a plate thickness of about 2 forms another seal line around the cylinder bore hole, and the bead or folded portion is formed. Absorbs irregularities on the opposite mounting surface, suppresses the amount of strain in the cylinder head that occurs during repeated combustion cycles, and reduces fluctuating load stress. Hesi serves to further prevent the total compression of the beads.

In such a metal gasket, a metal plate thinner than the metal plate is laminated on the outside of the bead in the radial direction except between the cylinder bore holes and on the convex side of the bead, and the folded portion and the bead in the radial direction. A structure that adjusts a step with the outer area, a step in which a soft metal plate is sandwiched between the folded portions when the step is less than or equal to a required step, and the folded portion is thick between the cylinder bore holes and Those that are thinly formed except between the cylinder bore holes to obtain a strong pressing force in the region between the cylinder bore holes where high sealing performance is required, and heat-resistant and oil-resistant non-metallic materials such as rubber or resin on both sides of the gasket. Apply to avoid direct metal-to-metal contact with the opposing mounting surface to prevent corrosion and stain on the metal surface, and ensure the sealing function regardless of the irregularities on the opposing mounting surface. It has proposed at the same time things.

Further, in the method of manufacturing a metal gasket, the step of forming a bore hole having an inner diameter smaller than that of the cylinder bore hole after completion of the molding in the elastic metal plate, and separating the bore hole from the peripheral edge of the bore hole in the radial direction outside, A step of forming a bead along the peripheral edge, a step of bending outwardly in the radial direction on the convex side of the bead around the bore hole to form a turn-back portion having a turn-up edge portion as a cylinder bore hole, the turn-back portion A step of applying a compressive force to the sheet to form it into a preset thickness, and a step of heat-treating the metal plate formed with the folded portion. The manufacturing method which adds the process of pinching a soft metal plate in the process of forming the said folding | returning part is also disclosed in the said manufacturing method.

[0008]

However, the above-mentioned metallic gasket proposed by the present applicant also has the following technical unsolved problems. That is,
The above-mentioned metal gasket basically includes an elastic metal plate having a folded portion formed by forming a bore hole having an inner diameter smaller than that of the completed cylinder bore hole and folding the bore hole radially outward around the bore hole. . Therefore, such an elastic metal plate has a structure in which the folded-back portion is completely folded back without a gap of 180 degrees at the folded-back edge portion serving as a cylinder bore hole, and undergoes severe stress changes during processing.
Cracks or cracks may occur in the folded-back portion, or even though heat treatment is performed, after tightening between the opposing mounting surfaces, it is exposed to repeated stress according to the combustion cycle for a long time and cracks occur in the folded-back edge portion that defines the cylinder bore hole. Is likely to occur.

Further, when the folded-back portion is formed around the cylinder bore hole, a step corresponding to the plate thickness is formed between the circumference of the cylinder bore hole and a region radially outside thereof. If the step is large, when the metal gasket is tightened between the cylinder head, the cylinder block and the opposing mounting surface, the elastic metal plate of the gasket body is forcibly deformed in the area inside and outside the step. In such a deformed region, stress is originally disadvantageous, and there is a risk that further unreasonable stress acts due to load fluctuations according to the combustion cycle of the internal combustion engine to cause cracks. Further, in the case of an elastic metal plate having a bead formed in a contour along the bore hole on the outer side in the radial direction with respect to the folded portion, if the thickness of the folded portion is large, a strong seal line is formed during tightening. Although it prevents the corrosive high temperature combustion gas from leaking from the cylinder bore hole, the role of the seal at the portion where the bead is formed is reduced accordingly. Therefore, the sharing of the seal is too biased toward the folded portion, and if the folded portion is damaged during long-term use, the bead seal, which is not so strong, effectively prevents the combustion gas from leaking. I can't do it.

When the step of the elastic metal plate due to the folded portion has a height larger than a desired height, a direction in which the height of the step of the folded portion is reduced by stacking the plate thickness adjusting plate on the elastic metal plate Although it is possible to adjust the adjustment plate, it is necessary to prepare an adjustment plate separately in such an adjustment method, which increases the manufacturing cost of the metal gasket and when manufacturing the adjustment plate, the beads of the elastic metal plate, etc. It is necessary to have a shape that matches the processed shape of (1), and there is a cumbersome and economical disadvantage that a step of laminating with an elastic metal plate and equipment therefor are required.

Further, since the folded-back end of the folded-back portion is not particularly subjected to processing such as chamfering, the leading-edge edge is in contact with the surface of the elastic metal plate, so that it is exposed to an environment where repeated stress acts for a long time, Cracks and scratch marks were formed on the surface of the elastic metal plate.

Further, also in the method of manufacturing a metal gasket, the metal gasket proposed in the above-mentioned prior application has limitations in the thickness, hardness and elongation characteristics of the elastic metal plate used. In other words, regarding the thickness of the elastic metal plate, the thickness of the folded portion is not adjusted in advance, so it is necessary to perform the folding process with the thickness of the adopted elastic metal plate, and the force required for processing is large. In the so-called pre-compression in which there is a risk of cracks, etc. that causes a sudden change in plate thickness at the folded edge, and the so-called pre-compression in which the plate thickness is adjusted by a press after folding, the adjustment amount becomes large and the plate thickness adjustment accuracy Since it is difficult to improve the flatness and the flatness, there are restrictions on the plate thickness that can be adopted.
Regarding the hardness of the elastic metal plate, it is difficult to fold it with a material having high hardness.
It is necessary to select and use the following elastic metal plates that are relatively soft and maintain a hardness that is easy to process, and this also limits the hardness of the elastic metal plate that can be adopted. Further, regarding the elongation characteristics of the elastic metal plate, if a material having poor elongation characteristics is used, cracks, cracks,
Strain or the like is likely to occur, and therefore, there is a constraint that an expensive elastic metal plate having good elongation characteristics must be adopted in order to prevent the occurrence of cracks, breakage, strain and the like.

Therefore, an object of the present invention is to solve the above-mentioned problems. Prior to forming the folded-back portion, the plate thickness of the region of the elastic metal plate on the folded inner surface side is made thin, It is possible to prevent cracks, breaks, distortions and the like from occurring in the folded-back portion of the elastic metal plate, for example, without compensating for an excessively large step due to the separate preparation of the adjusting plate, and the folded-back tip is made of the elastic metal plate. It is an object of the present invention to provide a metal gasket that does not cause scratches or cracks on the surface.

Another object of the present invention is to alleviate the restrictions on the material of the elastic metal plate in terms of thickness, hardness and elongation characteristics, and to make cracks or cracks in the folded portion during manufacturing in the folding step.
It is an object of the present invention to provide a method for producing a metal gasket, which can obtain a metal gasket with good quality and at low cost without causing distortion or the like.

[0015]

In order to achieve the above object, the present invention is configured as follows. That is, the present invention provides a metal gasket having a folded portion and an elastic metal plate forming a cylinder bore hole at the folded edge portion of the folded portion, wherein the inner surface side of the folded edge portion is provided along the cylinder bore hole. A first annular groove portion for thinning the elastic metal plate is formed, an annular hollow portion is formed in the annular groove portion on the inner surface side of the folded edge portion and folded back, and further, the folded tip of the folded portion is located. The present invention relates to a gasket made of metal, wherein a second annular groove portion that is thin is formed on the surface of an elastic metal plate.

In this metal gasket, another elastic metal plate is laminated on the elastic metal plate, and a bead is formed on the other elastic metal plate along the cylinder bore hole.
The convex portion of the bead and the folded-back portion of the elastic metal plate are arranged on opposite sides.

Further, in this metal gasket, the elastic metal plate is provided with a bead having a convex portion on the side of the folded portion along the cylinder bore hole.

Further, in this metal gasket, another elastic metal plate is laminated on the elastic metal plate, and a bead is formed along the cylinder bore hole on the other elastic metal plate,
The convex portion of the bead and the concave portion of the bead of the elastic metal plate are fitted in an aligned state.

Alternatively, according to the present invention, the step of forming a bore hole having an inner diameter smaller than that of the cylinder bore hole in the elastic metal plate, the bending region of the elastic metal plate is bent, and the folded edge is a cylinder bore hole. In the method for manufacturing a metal gasket, which includes a step of forming a folded portion, and a step of heat-treating the elastic metal plate having the folded portion formed therein, prior to the step of forming the folded portion, a folded side of the elastic metal plate. In the method for manufacturing a metal gasket, there is a step of processing an annular groove portion that thins a bending region on the inner surface side of the folded edge of the folded portion and a region where the folded tip of the folded portion is located.

Further, in this method for manufacturing a metallic gasket, there is a step of forming a bead having a convex portion on the side of the folded portion along the cylinder bore hole of the elastic metal plate.

Further, in this method for manufacturing a metal gasket, there is a step of laminating another elastic metal plate having a bead along the cylinder bore hole on the elastic metal plate.

[0022]

The metal gasket and the method for manufacturing the same according to the present invention are configured as described above, and operate as follows. That is, this metal gasket is a metal gasket having a folded-back portion in which the inner peripheral portion of the bore hole of the elastic metal plate is folded back so that the folded-back edge portion of the cylinder bore hole becomes a cylinder bore hole. Since the surface of the elastic metal plate facing the folded-back tip of the folded-back portion is partially thinned, it is made of metal between the opposed mounting surfaces of the internal combustion engine. When the gasket is sandwiched and tightened, the folded-back portions are not pressed against each other by the folded-back facing surfaces at the folded-back edge portions having a gap, and are not pressed against the elastic metal plate body even in the region of the folded-back tip. Therefore, it is the annular region between the folded edge portion and the folded tip that the folded portion contacts the elastic metal plate body, and the tightening force is shared and supported in this region.

At the folded edge, the gap is not absorbed by tightening the metal gasket, and the gap is secured even after the tightening is completed, so that the folded edge is not crushed or stress concentration occurs. Although the load fluctuation due to the operation of the internal combustion engine acts on the folded edge portion, the stress variation acting on the folded edge portion is alleviated. Furthermore, since the folded tip is not in contact with the elastic metal plate body, when the metal gasket is tightened and the internal combustion engine is in operation, the folded tip is dented on the surface of the elastic metal plate body by its edge. It does not cause scratches or scratches or cracks. In addition, the folded-back portion is a step with respect to the elastic metal plate body, but since the surface of the elastic metal plate on which the folded-back tip is located is recessed due to thinning, the thin-walled part is tightened between the opposing mounting surfaces. It can be bent from a position radially inward from the folded tip without interfering with, and bending stress generated in the elastic metal plate body at the step portion is reduced.

Alternatively, in the method for manufacturing a metal gasket according to the present invention, the step of forming a bore hole in the elastic metal plate, the folding region inside the folding edge of the folding portion and the folding region on the folding side of the elastic metal plate. The region where the folded-back tip of the portion is located, a step of forming a thin-walled portion, a step of performing a bending process at an intermediate position of the folded region to form a folded-back portion having the folded-back edge portion as a cylinder bore hole, and forming the folded-back portion. Since the method includes the step of heat-treating the metal plate, when the periphery of the bore hole formed in the elastic metal plate is folded back, the region to be folded which is the inside of the folded edge of the folded portion on the folded side of the elastic metal plate is thin in advance. Since it is formed in, the force required to fold it back is small,
Further, the folding is not performed 180 degrees abruptly and completely, but the metal material is gradually deformed. Therefore, when forming the folding edge, the metal material is less damaged and the residual concentrated stress is alleviated. . Further, since the region where the turn-back tip of the turn-back portion is to be positioned is also thinly formed in advance, the turn-back tip does not strongly press the surface of the elastic metal plate body to leave an indentation during the turn-back processing.

[0025]

Embodiments of the metal gasket and the method for manufacturing the same according to the present invention will be described below with reference to the drawings. FIG. 1 is a partial plan view showing an embodiment of a metal gasket according to the present invention.

The metal gasket 1 shown in FIG. 1 is used, for example, to seal opposing mounting surfaces of a cylinder head and a cylinder block (neither shown) in a multi-cylinder engine such as a six-cylinder engine. Is.
The metal gasket 1 is made of a single plate or a plurality of elastic metal plates, and the thickness t is 0.
Values between 10 mm and 0.30 mm have been selected.
Conventionally, in order to perform a folding process, it was necessary to use a soft metal material having a hardness before quenching up to Hv200, but according to the present invention, the elastic metal plate 3 is made of Hv.
It can be processed using a material having a hardness up to v350.

Elastic metal plate 3 in the metal gasket 1
Are formed in the multi-cylinder engine, that is, the number of cylinder bores 2A, 2B, 2C, ... Is the number of holes corresponding to the number of cylinder bores formed in the cylinder block. Reference numeral 2 is used). Further, the elastic metal plate 3 of the metal gasket 1 has an oil hole and an oil return hole 16 for passing oil, a bolt hole 17 for inserting a bolt for fastening the metal gasket 1 between opposed mounting surfaces, and a water hole for passing cooling water. 18, dowel hole,
A plurality of rivet holes and the like are provided. Although not shown,
In the cross section passing through each hole, the elastic metal plate 3 has a conical shape or a trough shape surrounding the holes around these holes, and when the metal gasket 1 is tightened, the elastic metal plate 3 surrounds these holes. It is designed to be sealed. Since each of these holes is a well-known technique in the technical field of metal gaskets, detailed description thereof is omitted here.

Although not shown, for both the front and back surfaces of the metal gasket 1, a non-metal material such as heat-resistant and oil-resistant rubber (for example, fluororubber), resin, etc., for example, having a thickness of 10 μm. By applying a coating of about 50 μm, it is possible to avoid a metal-to-metal contact state with the cylinder head and the cylinder block, and to secure corrosion resistance, durability and strength as a gasket.
Even if the metal gasket 1 itself and the machined surfaces such as the opposing mounting surfaces of the cylinder head and the cylinder block have irregularities, the non-metallic material can cover the irregularities and perform a sufficient sealing function. The application of the non-metallic material is preferably completed after forming the bore hole and adjusting the thickness of the elastic metal plate and before starting the bending process.

FIG. 2 is a sectional view taken along the line AA in FIG. 1, FIG. 3 is an enlarged view of a folded portion which is a part of FIG. 2, and FIG. 4 is a developed view of an elastic metal plate having a folded portion. is there. Figure 2
Is a cross section of the metal gasket 1 obtained by cutting a boundary portion between adjacent cylinder bore holes 2A, 2B, 2C ... Formed in the elastic metal plate 1 by a line AA connecting the centers of the cylinder bore holes 2A, 2B. That is, the cross section between the cylinder bore holes 2 is shown, but it goes without saying that the boundary portion between other adjacent cylinder bore holes 2 also has the same cross sectional structure.

As can be understood from these drawings, the metal gasket 1 is composed of a single elastic metal plate 3. For the elastic metal plate 3, the thickness t is about 0.10 to
A bead 4A, 4B having a cross-sectional chevron or concavo-convex portion which is in the range of 0.30 mm, for example, has a thickness of about 0.25 mm, and which surrounds the peripheral portion of the cylinder bore 2 concentrically with the cylinder bore 2 and annularly. 4C are formed (reference numeral 4 indicates a generic name for the bead, like the cylinder bore hole 2). The bead 4 has cylinder bore holes 2A and 2B.
In the region between the adjacent cylinder bores such as the space, the beads 4 are associated with each other. While the distance from the cylinder bore hole 2 becomes gradually shorter at the meeting portion of the beads 4,
As described above, the width of the bead 4 is narrow. However, when the distance between the cylinder bore holes 2 is sufficient, the adjacent beads 4 may be arranged with a slight gap therebetween without overlapping each other. In the illustrated example, bead 4
Is a distance L ₂ from the inner peripheral edge of the cylinder bore hole 2 (for example,
Starting from about 2.0 mm), the predetermined width L _{3 in} the radial direction is about 2 mm in the region between the cylinder bore holes and about 2.5 mm in the region other than between the cylinder bore holes. The bead 4 in the area other than between the cylinder bores is 5 m
The top of the convex side is formed substantially flat with a width of m to stabilize the contact between the bead 4 and the opposing mounting surface, although the spring constant is slightly lowered. The height H of the bead 4 is about 0.25 mm, which is the thickness of the elastic metal plate 3. The diameter of the cylinder bore hole is 87 mm, and the distance L ₁ between the adjacent cylinder bore holes 2 is, for example, about 6.0 mm.

The elastic metal plate 3 has folded-back portions 5A, 5B, 5C (hereinafter, reference numeral 5 is used when referring to the folded-back portions) at the peripheral edge of the cylinder bore hole 2. The folded-back portion 5 is formed so as not to overlap the bead 4 on the convex surface side of the bead 4 and on the radially inner side of the bead 4. The radial width of the folded portion 5 of the elastic metal plate 3, that is, the folded width L ₄ is, for example, about 1.5 mm.

As shown in FIG. 3 in which the folded-back portion 5 is enlarged,
In the region of the folded edge portion 7 of the folded portion 11, a circumferential groove portion, that is, an annular groove portion 6 is formed and thinned, and an annular hollow portion, that is, a gap 14 is formed and folded back. In the region outside the gap 14 in the radial direction of the cylinder bore 2, the folded inner surface 12 of the folded portion 11 is in contact with the non-thinned surface 10 of the elastic metal plate body. Further, since the portion 9 of the elastic metal plate body to which the folding tip 13 of the folding portion 5 faces is partially thinned from the folding surface side and formed in the circumferential groove portion, that is, the annular groove portion 8, the folding tip 13 is It is not in contact with the surface of the elastic metal plate 3.

The metal gasket 1 is interposed between the cylinder head and the cylinder block. For example, when the metal gasket 1 is tightened by a bolt passing through the bolt hole 17 to be pressed, the bead 4 of the elastic metal plate 3 and the folded portion. 5 contacts the opposing mounting surface to form a double annular seal around the cylinder bore 2. These two-staged annular seal portions prevent the high-temperature and high-pressure combustion gas from the cylinder bore 2 from leaking out to the opposing mounting surfaces. In addition, when the cylinder head and the cylinder block are tightened, even if the opposing mounting surfaces of the cylinder head and the cylinder block are irregular, the folded-back portion 5 and the bead 4 are correspondingly deformed, and as described above. Absorbs uneven gaps in combination with an increase in the number of seals. The folding part 5 is a bead 4
At the same time, the tightening force is supported in a shared manner, and the bead 4 is prevented from being compressed by the thickness of the folded-back portion 5, so that the bead 4 is prevented from being set. Further, due to the increase in the annular seal portion and the absorption of the irregularity of the facing mounting surface, the amount of distortion of the cylinder head that is repeatedly generated during the combustion cycle of the explosion / expansion stroke of the internal combustion engine is suppressed, and the occurrence of cracks in the seal portion is prevented. Can be prevented. The function of the metal gasket 1 is the same as the conventional one.

When the metal gasket 1 as described above is sandwiched between the opposing mounting surfaces of the internal combustion engine and tightened, the folded-back portion 5 is formed.
Then, the tightening force is shared and supported by the elastic metal plate 3, that is, the annular region formed of the surface 10 in contact with the elastic metal plate body, and the elastic metal plate 3 is provided in the region of the folded edge 7 and the folded tip 13 having the gap 14. Not pressed against the body,
Even if they come into contact with each other, the pressing force is sufficiently small. Therefore, in the folded edge portion 7, the gap 14 is not absorbed by the tightening of the metal gasket 1 and the gap 14 is secured even after the tightening is completed, so that the folded edge portion 7 is not crushed or stress concentration occurs. , Therefore metal gasket 1
No cracks or distortions are generated in the folded edge portion 7 with tightening. Further, although the load fluctuation due to the operation of the internal combustion engine also acts on the folded edge portion 7, the stress variation acting on the folded edge portion 7 is alleviated, and the folded edge portion 7 is used even during long-term use.
It does not cause cracks, strains, or cracks. Further, since the folded-back tip 13 is not in contact with the elastic metal plate body due to the circumferential groove portion 8 which is a recessed portion, the folded-back tip 13 is not tightened when the metal gasket 1 is tightened and the internal combustion engine is operating. The edges do not cause indentations, scratches or cracks on the surface of the elastic metal plate body.

Although the folded-back portion 5 forms a step with respect to the elastic metal plate body, the surface of the elastic metal plate 3 on which the folded-back tip 13 is located is formed into an annular groove portion 8 by thinning. When the metal gasket 1 is tightened between the opposing mounting surfaces, the elastic metal plate 3 is deformed so as to eliminate such a step, but the elastic metal plate 3 is an annular region located radially inward of the folded tip 13. Since it can be bent from the starting position of the thin portion 9, the bending stress generated in the elastic metal plate body at the step portion is reduced.

The metal gasket according to the present invention has the above-mentioned structure, but the metal gasket 1 can be manufactured by the manufacturing method including the following steps. This manufacturing method will be described with reference to a development view showing a state before folding back of the elastic metal plate 3 shown in FIG.

First, the bore hole 15 is formed in the elastic metal plate 3 in a radius smaller than the desired cylinder bore hole 2 by a predetermined length. When the bending is completed, the bore hole 15 is provided with a folded-back tip 13
It is a hole that becomes. Here, the cylinder bore hole 2 and the bore hole 1
5 has the same hole center. Further, various holes such as the bolt holes 17 other than the cylinder bore hole 2 are formed by punching. Next, the folded width L ₄ is radially outward from the peripheral edge of the bore hole 15.
The annular region 7 having a predetermined width L ₅ (0.6 mm in the illustrated example) centering on the portion of the distance of (6) and the portion where the folded tip 13 is located (distance from the bore hole 15 to twice the folded width L ₄ ) The annular region 9 having a predetermined width L ₆ (0.6 mm in the illustrated example) is formed thinly around the position (1) to form the annular groove portions 6 and 8, respectively. The thinning is performed from the surface of the elastic metal plate 3 on the folded side. A predetermined interval (0 .. in the example shown in the figure is provided between the thin portion 7 of the annular region and the thin portion 9 of the annular region.
5 mm), a region without thinning is formed.
The thinning depth d is 0.02 mm in the illustrated example.

Further, for forming the annular groove portions 6 and 8 in the elastic metal plate 3, thinning may be carried out by any processing method such as press molding, etching processing and cutting processing. In the case of press molding, it is possible to perform press molding at the same time as punching of the bore hole 15. Next, the bead 4 is formed in the elastic metal plate 3 along the cylinder bore hole 2, and the folded width L ₄ around the bore hole 15 to the center line of the annular groove portion 6 is formed.
The fold-back portion 1 having the fold-back portion 1 is subjected to a bending process outward in the radial direction on the surface side having a reduced thickness.
The surface 12 of 1 is brought into contact with the surface 10. Folded tip 13
Are brought into the central position of the annular groove 8 or the thinned annular region. When the bending process is completed, the folded-back portion 5 having the cylinder bore hole 2 on the inner circumference of the folded-back folded edge portion 7 is formed. Finally, the elastic metal plate 3 on which the folded-back portion 5 is formed is heat-treated to cure the elastic metal plate 3, whereby the metal gasket 1 having appropriate elasticity can be manufactured.

After the bending process for forming the folded-back portion 5 and before heat-treating the metal gasket 1, a compressive force is applied to the folded-back portion 5 in the plate thickness direction to set a preset thickness. It is possible to perform a step of slightly deforming up to. That is, the cylinder head has a lower rigidity than that of the cylinder block, and in a multi-cylinder engine, a portion between the adjacent cylinder bore holes 2 is likely to be most distorted due to load fluctuations in a combustion cycle of an internal combustion engine in an explosion stroke and an expansion stroke. By the way. Therefore, since the sealing function of the metal gasket is most likely to deteriorate in this portion, the sealing performance in the region between the cylinder bore holes 2 of the folded portion 5 is stronger than the sealing performance in the region other than between the cylinder bore holes 2. In order to achieve this, it is conceivable that the plate thickness of the folded-back portion 5 located in the region between the cylinder bore holes 2 is made thicker than the plate thickness of the folded-back portion 5 located in the region other than between the cylinder bore holes 2. Therefore, after the bending process of the folded-back portion 5, the folded-back portion 5 located in the region other than between the cylinder bores 2 is positioned between the cylinder bores 2.
A step of applying a compressive force for deforming a larger amount may be provided.

Specifically, as shown in FIGS. 10 and 11, the region a between the cylinder bores 2 is formed to have the largest thickness, and the regions b extending on both sides of the region a are thick. Gradually decreases, and further, the thickness is formed thinnest in the region c of the arc portion extending on both sides thereof. In addition, the elastic metal plate 3 having the folded-back portion 5 is formed.
Is hardened by heat treatment. At this time, the hardness is Hv 350 or less before the bead formation, and after the heat treatment, the hardness according to the type of the elastic metal plate 3 (for example, about Hv 500).
To be cured.

FIG. 5 is a sectional view in the region between the cylinder bore holes showing another embodiment of the metal gasket according to the present invention. The metal gasket of this embodiment is composed of two elastic metal plates. Metal gasket 20
Is an elastic metal plate 3 having the folded-back portion 5 and an elastic metal plate 2 having a bead 24 having a thickness larger than that of the elastic metal plate 3.
It consists of 1. That is, another elastic metal plate 21 is laminated on the elastic metal plate 3, and a bead 24 is formed along the cylinder bore hole 22 in the elastic metal plate 21, and the convex portion of the bead 24 and the elastic metal plate 3 are formed. It is located on the side facing the folded-back portion 5. The elastic metal plate 3 has a thickness of about 0.12 mm.
The positions of the cylinder bore holes 22, 22 of the elastic metal plate 21 are completely aligned with the cylinder bore holes 2, 2 of the elastic metal plate 3. In the folding unit 5, the same components as those in the previous embodiment are designated by the same reference numerals, and there is no functional change, so redundant description will be omitted. The fold-back portion 5 of the elastic metal plate 3 is fold-backed on the bead 24 side of the elastic metal plate 21, and when the metal gasket 20 is fastened, the fold-back portion 5 shares and supports the fastening force together with the bead 24, and the bead 24 is also supported. Prevents full compression of 24 and prevents settling of beads 24.

FIG. 6 is a sectional view in the region between the cylinder bore holes showing another embodiment of the metal gasket according to the present invention. This metal gasket is composed of two elastic metal plates, an elastic metal plate 3 having a folded portion 5 and an elastic metal plate 31 having a bead 34 having a thickness larger than that of the elastic metal plate 3. This metal gasket 30 is
Another elastic metal plate 31 is laminated on the elastic metal plate 3, and a bead 34 is formed in the elastic metal plate 31 along the cylinder bore holes 32, 32, and a convex portion of the bead 34 has an elastic metal plate 3
Is fitted in the concave portion of the bead 4 in an aligned state. The elastic metal plate 31 has the same structure as the elastic metal plate 21 of FIG.
The elastic metal plate 3 forming the folded-back portion 5 has the same plate thickness as the elastic metal plate 3 of FIG. 5, but the beads 4 are formed in conformity with the bead shape of the elastic metal plate 31. Therefore, when the two elastic metal plates 3 and 31 are overlapped with each other, there is no gap between the two elastic metal plates 3 and 31 and they are in an aligned state. The folding direction of the folding portion 5 is the convex side of the bead 4, and supports the sharing of the tightening force of the metal gasket 30, the complete compression of the bead and the prevention of the settling, the irregular absorption of the opposing mounting surface, and the fluctuation during the operation of the internal combustion engine. Basic functions such as prevention of cracks due to load are as described above.

FIG. 7 is a sectional view in the region between the cylinder bore holes showing another embodiment of the metal gasket according to the present invention. The metal gasket 40 is composed of two elastic metal plates, each of which is composed of an elastic metal plate 3 having a folded portion 5 and an elastic metal plate 41 having a bead 44 thicker than the elastic metal plate 3. ing. Elastic metal plate 4
1 is a bead 44 formed along the cylinder bore hole 42 similarly to the elastic metal plate 21 of FIG. 5 and the elastic metal plate 31 of FIG.
It has a structure with. The elastic metal plate 3 forming the folded-back portion 5 has a plate thickness similar to that of the elastic metal plate 3 of FIG. 5, that is, about half of the elastic metal plate 41, but faces the bead 44 at a position opposed to the bead 44. Bead 4
Is formed. The bead 4 has a bead width wider than that of the bead 44, but the top of the bead is formed flat so as to absorb the positional deviation with the bead 44 and stabilize the convex contact of the bead. The structure of the folded portion 5 is the same as that in FIG. When the metal gasket 40 is tightened between the opposing mounting surfaces, the hem regions of the beads 4 and 44 and the folded-back portion 5 make strong sealing contact with the opposing mounting faces, but the elastic metal plate 3 having a thin plate thickness is first. Reach the yield point with a small force,
Next, since the elastic metal plate 41 having a large plate thickness starts to bend, it exhibits preferable spring characteristics according to the tightening process. Folding part 5
Is folded back to the convex side of the bead 4, and supports the metal gasket 40 in sharing the tightening force, completely compresses the bead and prevents settling, absorbs imperfections in the opposing mounting surface, and cracks due to fluctuating load during operation of the internal combustion engine. The basic functions such as prevention are as described above.

FIG. 8 is a sectional view in the region between the cylinder bore holes showing another embodiment of the metal gasket according to the present invention. The metal gasket 50 is composed of three elastic metal plates. The embodiment of the metal gasket 50 corresponds to the metal gasket 50 in which another elastic metal plate is laminated on the metal gasket 30 of FIG. 6 so that the bead portions face each other. Outer elastic metal plates 51, 5
5 has a structure having beads 54 and 56, like the elastic metal plate 21 of FIG. 5 and the elastic metal plate 31 of FIG. Bead 5
4, 56 are arranged on the sides whose convex sides face each other.
The elastic metal plates 3 forming the folded portion 5 are both elastic metal plates 5.
The elastic metal plate 51 is arranged between the first and the second portions 55 and 55, and is laminated without gaps on the elastic metal plate 51 in the same bead shape as the metal gasket 30 shown in FIG. Elastic metal plate 5
1,55 cylinder bore holes 52,52 and 53,53
Are aligned with the cylinder bore holes 2 and 2 of the elastic metal plate 3. In addition to the strong sealing function of the two outer elastic metal plates 51, 55 having a large plate thickness, the metal gasket 50 supports the tightening force in a shared manner, completely compresses the bead and prevents the settling, and absorbs the irregularity of the opposite mounting surface. The basic functions such as prevention of cracks due to fluctuating load during operation of the internal combustion engine are the same as the above example.

FIG. 9 is a sectional view in the region between the cylinder bore holes showing still another embodiment of the metal gasket according to the present invention. The metal gasket 60 is composed of three elastic metal plates. Metal gasket 60
Is a pair of two bead substrates composed of elastic metal plates 61, 65 having beads 64, 67 formed along the parallel cylinder bore holes 62, 72, and two tops of the beads 4, 69 symmetrically contacting each other. It is a laminated metal gasket in which an intermediate plate composed of elastic metal plates 3 and 68 is laminated. A step 7 that is less than the thickness of the elastic metal plate 3 that is the second intermediate plate is formed along the cylinder bore holes 70 of the elastic metal plate 68 that is the first intermediate plate.
1, 71 are formed, and the elastic metal plate 3 is laminated on the outer surface which is convex due to the formation of the steps 71, 71. The folded-back portions 5 and 5 of the elastic metal plate 3 have the steps 7 formed on the first intermediate plate.
Folded back to the side of the cylinder bores 1 and 71, a compensating portion is formed around the cylinder bores 2 and 70, which is thicker than the total thickness of the two intermediate plates at the portions where the tops of the beads 4 and 69 contact. This compensator improves the surface pressure balance when tightening between opposing mounting surfaces, reduces stress fluctuations on the bead board and bending stress on the compensator, and prevents damage to the bead and compensator and a reduction in sealing effect. Then, it exerts a stable sealing effect even under severe conditions for metal gaskets such as diesel engines.

[0046]

Since the metal gasket and the method for manufacturing the same according to the present invention are configured as described above, they have the following effects. That is, the metal gasket according to the present invention is a metal gasket provided with a folded-back portion obtained by folding back the inner peripheral portion of the bore hole of the elastic metal plate so that the folded-back edge portion becomes the cylinder bore hole. Since the surface of the elastic metal plate facing the folded-back tip of the folded-back portion is partially thinned, the metal gasket fastening force sharing support and the bead are formed. In the case of including an elastic metal plate having a basic bead, it is possible to prevent the bead from being completely compressed and settled, and to prevent the irregular mounting and distortion of the opposing mounting surface, especially the cylinder head, and reduce the fluctuating load during operation of the internal combustion engine. In addition to the effects, the following effects peculiar to the present invention are achieved.

That is, when the metal gasket is sandwiched between the opposing mounting surfaces of the internal combustion engine and tightened, the folded inner edges are not pressed by the folded edge portions having the gap of the folded portions, and the elasticity is also provided in the region of the folded tip. It is not pressed against the metal plate body. Therefore, it is the annular region between the folded edge portion and the folded tip that the folded inner surface contacts at the folded portion, and the tightening force is shared and supported in this region. At the folded edge, the gap is not absorbed by tightening the metal gasket, and the gap is secured even after the tightening is completed. Therefore, the folded edge portion is not crushed and stress concentration does not occur, and the folded edge portion is not cracked or wrinkled when the metal gasket is tightened. Further, the load fluctuation accompanying the operation of the internal combustion engine also acts on the folded edge, but the stress fluctuation is absorbed and relaxed in the contacting annular region, and the folded edge does not cause cracks or wrinkles even during long-term use. . Furthermore, since the folded tip is not in contact with the elastic metal plate body, when the metal gasket is tightened and the internal combustion engine is in operation, the folded tip is dented on the surface of the elastic metal plate body by its edge. It does not cause scratches or scratches or cracks.

On the other hand, in the method of manufacturing a metal gasket of the present invention, the step of forming a bore hole having an inner diameter smaller than that of the cylinder bore hole at the time of completion of formation in the elastic metal plate,
On the folding side of the elastic metal plate, a step of thinly forming a region to be folded and a region where the folded tip of the folded portion is to be located inside the folded edge of the folded portion, at an intermediate position of the region to be folded. When folding the periphery of the bore hole formed in the elastic metal plate, it includes a step of performing a bending process to form a folded portion having a folded edge portion as a cylinder bore hole and a step of heat-treating the metal plate on which the folded portion is formed. In addition, since the region to be folded for the folded portion is formed thin in advance on the folded side of the elastic metal plate, the force required for folding is small, and the folding is performed 180 degrees rapidly and completely. Rather, it is a process in which the metallic material gradually deforms. Therefore, there is little damage to the metal material when forming the folded edge portion,
Moreover, the residual concentrated stress is also relaxed. Further, since the region where the turn-back tip of the turn-back portion is to be positioned is also thinly formed in advance, the turn-back tip does not strongly press the surface of the elastic metal plate body to leave an indentation during the turn-back processing.

Further, as described above, the metal gasket proposed in the above-mentioned prior application is limited in the thickness, hardness and elongation characteristics of the elastic metal plate to be used, but the metal gasket according to the present invention is used. Such a limitation can be relaxed by the method of manufacturing the gasket. That is, regarding the plate thickness of the elastic metal plate, since the folded-back portion is thinned to such an extent that the folded-back edge portion which is a direct portion for bending work is easily worked, the force required for working is small and Since the bending angle is relatively slow and there is no sudden material deformation, there is no risk of cracks, and in the case of so-called precompression in which the plate thickness is adjusted later by pressing etc., the adjustment amount becomes large. However, since it is easy to ensure plate thickness adjustment accuracy and flatness,
The restrictions on the plate thickness that can be adopted are relaxed.

Regarding the hardness of the elastic metal plate, since the bending process can be performed by a relatively slow material deformation, if the hardness is Hv 350 or less before the folding process, even a material having high hardness can be bent. In this respect as well, the restriction on the hardness of the elastic metal plate that can be adopted is relaxed, and the range of choices of usable metal materials is expanded.

Further, regarding the elongation characteristics of the elastic metal plate,
Since the degree of elongation required during bending is small, cracks and wrinkles are less likely to occur at the folded portion even if a material with poor elongation properties is used.Therefore, elongation properties are required to prevent cracks and wrinkles from occurring. It is not necessary to use an expensive and expensive elastic metal plate, an inexpensive elastic metal plate can be used, and the restriction on the elongation characteristics of the elastic metal plate is relaxed. And finally, in the method for manufacturing a metal gasket according to the present invention,
It is possible to relax the restrictions on the material of elastic metal plate in terms of thickness, hardness and elongation characteristics, to prevent cracks and wrinkles in the folded part during manufacturing, and to obtain a metal gasket with good quality and at low cost. .

[Brief description of drawings]

FIG. 1 is a partial plan view showing an embodiment of a metal gasket according to the present invention.

FIG. 2 is a cross-sectional view taken along line AA of FIG. 1 showing this metallic gasket.

FIG. 3 is an enlarged cross-sectional view showing a folded portion that is a part of FIG.

FIG. 4 is a partial development view of an elastic metal plate forming a folded portion shown in FIG.

FIG. 5 is a partial cross-sectional view showing between the cylinder bore holes of another embodiment of the metal gasket according to the present invention.

FIG. 6 is a partial cross-sectional view showing a space between cylinder bores of another embodiment of the metal gasket according to the present invention.

FIG. 7 is a partial cross-sectional view showing between the cylinder bore holes of another embodiment of the metal gasket according to the present invention.

FIG. 8 is a partial sectional view showing a space between cylinder bores of a metal gasket according to another embodiment of the present invention.

FIG. 9 is a partial cross-sectional view showing between the cylinder bore holes of another embodiment of the metal gasket according to the present invention.

FIG. 10 is an explanatory diagram showing the distribution of the thickness of the folded portion around the cylinder bore holes located at both ends of the metal gasket.

FIG. 11 is an explanatory diagram showing the distribution of the thickness of the folded portion around the cylinder bore holes located at other than both ends of the metal gasket.

[Explanation of symbols]

1, 20, 30, 40, 50, 60 Metallic gasket 2, 22, 32, 42, 52, 53, 62, 70, 72
Cylinder bore hole 3,21,31,41,51,61,65 Elastic metal plate 4,24,34,44,54,56,64,67 Bead 5 Folded part 6,8 Annular groove part 7 Thin part of bent edge part 9 Thin-walled part where the folded tip is located 10 Surface of elastic metal plate 11 Folded part 13 Folded tip 14 Gap 15 Bore hole

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kunitoshi Inoue 248 Kano, Higashiosaka City, Osaka Prefecture Japan Gasket Co., Ltd.

Claims (7)

[Claims] 1. A metal gasket comprising a folded-back portion and an elastic metal plate forming a cylinder bore hole at a folded-back edge portion of the folded-back portion, wherein the inner surface of the folded-back edge portion extends along the cylinder bore hole. A first annular groove portion for thinning the elastic metal plate is formed, an annular hollow portion is formed in the annular groove portion on the inner surface side of the folded edge portion and folded back, and further, the folded tip of the folded portion is located. A metal gasket, wherein a second annular groove portion for thinning is formed on the surface of the elastic metal plate. 2. Another elastic metal plate is laminated on the elastic metal plate, and a bead is formed along the cylinder bore hole on the other elastic metal plate, and the convex portion of the bead and the elastic metal plate are formed. The metal gasket according to claim 1, wherein the metal gasket is arranged on a side facing the folded-back portion. 3. The metal gasket according to claim 1, wherein the elastic metal plate is provided with a bead having a convex portion on the folded portion side along the cylinder bore hole. 4. Another elastic metal plate is laminated on the elastic metal plate, and a bead is formed along the cylinder bore hole on the another elastic metal plate, and the convex portion of the bead and the elastic metal plate are formed. The metal gasket according to claim 3, wherein the metal gasket is fitted in the concave portion of the bead in an aligned state. 5. A step of forming a bore hole having an inner diameter smaller than that of the cylinder bore hole in the elastic metal plate, and a bending region of the elastic metal plate is bent to form a folded portion having a folded edge portion as a cylinder bore hole. In the method for manufacturing a metal gasket, which comprises a step, and a step of heat-treating the elastic metal plate having the folded portion formed thereon, prior to the step of forming the folded portion, the folded portion on the folded side of the elastic metal plate. 2. A method for manufacturing a metal gasket, comprising a step of processing an annular groove portion that thins a bending region on the inner surface side of the folded edge portion and a region where the folded tip of the folded portion is located. 6. The method of manufacturing a metal gasket according to claim 5, further comprising a step of forming a bead having a convex portion on the side of the folded portion along the cylinder bore hole of the elastic metal plate. 7. The method of manufacturing a metal gasket according to claim 5, further comprising a step of laminating another elastic metal plate having a bead on the elastic metal plate along a cylinder bore hole.